Corrugated tubing or metal hose provides an alternative to rigid piping systems as a conduit for transporting fluids such as natural gas. The corrugated tubing can be easily installed and is useful in many system applications. Corrugated tubing allows for simpler more cost-effective installation due to its uniquely flexible structure and relatively high strength. The same flexibility has inherent limitations. As the internal pressure of the working fluid inside the tubing is increased the corrugated tubing structure reacts to the pressure. The typical corrugated tubing structure begins to spread and expand along its length when the internal pressure overcomes the strength of the tubing material. The higher pressures of the working fluid cause the corrugations to expand. The corrugation expansion results in a distortion of the tubing out of its original shape and size.
In order to meet higher operating pressure ranges, conventional corrugated tubing may be sleeved with a wire braid. The braid is fixed at opposite ends of the corrugated tubing. The braid reinforces the corrugated tube structure thereby resisting the expansion of the corrugations when the internal pressure is increased. The braid is effective in the function of resisting the expansion of the corrugated tubing thereby increasing operational pressure capability. However, the braid covering the corrugated tubing outer diameter is subject to relative motion with the corrugated tubing that it covers. The tubing and the braid move relative to each other along the length of the corrugated tubing. In applications that plumb the corrugated tubing to mechanical equipment that create vibration translated to the tubing, the relative motion causes abrasion between the inside of the braid and the outer surface of the tubing. The abrasion between the tubing outer surface and the braid inner surface creates failure mechanisms that compromise the integrity of the corrugated tubing structure. The braid saws and rubs off the outer surface material of the corrugated tubing until the tubing pressure boundary fails and subsequently leaks the working fluid.
Another drawback to existing tubing is that the tubing is often contained within a jacket. Typically, the jacket is made from an insulative material. In the event that the piping is introduced to an electrical charge (e.g., from direct or indirect lightning), charge accumulates on the jacket and can burn through the jacket to the tubing resulting in a breach of the tubing.